Apparatus for salvaging and removing marine oil spills

ABSTRACT

This invention relates to a novel apparatus for cleaning and salvaging oil spills in marine environments. The invention is directed to a dual purpose vessel adapted for use in sand dredging and oil spill clean-up comprising: (a) a hull; (b) at least two pump suction tubes mounted to the exterior of the hull, the suction tube inlets being located below the water line of the hull, and being rotatably connected to the hull; (c) a draghead which is adapted to ride in part above the water level attached at the end of each suction tube opposite the suction tube inlet connection; (d) a buoyancy compensator cooperating with the draghead to ensure that at least part of the draghead rides above the water level at all times; and (e) separation of the oil from the water by directing two opposing streams of the collected oil/water mixture against each other above a container.

This is a divisional of copending application Ser. No. 07/522,988 filedon May 14, 1990.

FIELD OF THE INVENTION

This invention relates to a novel apparatus for cleaning and salvagingoil spills in marine environments.

BACKGROUND OF THE INVENTION

Oil spills from petroleum transporting marine vessels cause tremendousenvironmental damage. The Andrea Dorea oil spill in the English Channelin the 1970's killed wildlife in the hundreds of thousands, createdtremendous hardship for fishermen in the damaged area and fouled thebeaches of France and England for at least ten years.

Recently, the Exxon Valdez, an oil tanker owned by Exxon Corporation,ran aground on a reef in the Gulf of Alaska and spilled tens of millionsof gallons of crude oil into the ocean with staggering loss of wildlifeand marine life such as sea birds, sea otters, seals, salmon andshellfish. It is estimated that it will take years before the damage isrectified. Efforts by Exxon to contain the spill and clean up the oilwere pitiful. After much effort, only about 10,000 barrels of crude wererecovered.

U.S. Pat. No. 4,394,265, granted Jul. 19, 1983, discloses a suctiondredger that is provided with sweeping arms at the side of the vessel.The arms can be placed at an angle with respect to the body of thevessel and are provided with suction apparatus to suck away the upperlayer of the water collected in front of the sweeping arms. The water ispumped into the hold of the vessel so that the hold optionally can beused for storing dredging material or oil respectively. Apparatusconnects the sweeping arms to the vessel and moves the arms from aninward storage position into an outboard operative position and viceversa. The sweeping arms are in a tilted position when inboard and ifnecessary displaceable in the longitudinal direction of the vessel alongits deck so that in the case of a suction dredger the normal dredgingapparatus performs its function without being hampered by the sweepingarms. The apparatus is constructed so that the sweeping arms can beapplied to any type of vessel.

SUMMARY OF THE INVENTION

The invention is directed to a dual purpose vessel adapted for use insand dredging and oil spill clean-up comprising: (a) a hull; (b) atleast two pump suction tubes mounted to the exterior of the hull, thesuction inlets being located below the water line of the hull, and eachbeing pivotally associated with the hull; (c) at least two dragheadswhich are adapted to ride in part above the water level and are attachedat the respective ends of the suction tubes opposite the suction-hullinlet; and (d) at least two buoyancy floats secured to the respectivedragheads to ensure that at least part of each draghead rides above thewater level.

A vessel as described wherein the draghead and float are connected to ahull connected swell compensator which assists in maintaining a part ofthe draghead above water surface level. A vessel as described whereinthe suction tube is raised and lowered by means of a hull mounted winchand cable system which is connected to the suction tube.

A vessel as described wherein a suction pump is positioned in theinterior of the hull, and is connected to the suction inlet of thesuction tube, the discharge of the suction pump being connected to adischarge tube which discharges material pumped by the suction pump tothe interior of the vessel.

In the vessel as described, the hull may have in the interior thereof atleast one hopper into which material pumped by the suction pump isdischarged, the hopper having the capacity to discharge at least some ofthe discharged material through the bottom of the hull. In the vessel, aplurality of hoppers can be disposed in the hull and material pumpedinto the main hopper can overflow into adjacent hoppers in the vessel,the main discharge hopper being isolated from the adjacent hoppers.

A vessel as described wherein a suction tube is mounted on each side ofthe hull, each suction tube being connected to a respective pump, andeach pump having a separate discharge tube, both discharge tubesdischarging material into the main hopper. In the vessel, the dischargefrom the two discharge tubes can be directed at one another to assist inseparating oil from the water in the discharge material.

A vessel as described wherein the hull can be fitted with baffles whichassist in directing material pumped from the pair of discharge tubesinto the main material hopper. In the vessel, the draghead swellcompensator can be hydraulically operated.

DRAWINGS

In drawings which depict specific embodiments of the invention but whichshould not be construed as limiting or restricting the scope of theinvention in any way:

FIG. 1 illustrates a side view of a vessel fitted with an oil slickdraghead;

FIG. 2 illustrates a detail side view of a draghead with buoyancy;

FIG. 3 illustrates a side cut-away view of a vessel exposing theoil/water hold tanks;

FIG. 4 illustrates a top view of the oil/water hold tanks of the vessel;

FIG. 5 illustrates an enlarged cut-away side view of the oil/water holdtanks;

FIG. 6 illustrates a side view of a swell compensator for the floatationsuction draghead with buoyancy; and

FIG. 7, which appears on the same sheet as FIGS. 1 and 2, illustrates atop view of the floatation suction draghead.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

A specific embodiment of the invention is disclosed in FIGS. 1 to 7.Referring to FIG. 1, which illustrates a side view of a vessel fittedwith an oil slick suction flotation draghead, it can be seen that thevessel 2 has disposed along the side thereof an elongated two partsuction tube 4. The two part suction tube 4 is connected at one end tothe hull of the vessel 2 below the water line by a water-tight sand pumpsuction inlet 6. The aft section of the suction tube 4 is universallypivotally connected by means of a universal coupling 8 to theforesection of the tube 4. The pivot direction is indicated by arrows5-5. The universal coupling 8 and the inlet 6 are suspended by winchcables 14. The aft section end of the suction tube 4 opposite sand pumpsuction inlet 6 has attached thereto a floatation draghead 10. Thedraghead 10 is suspended in place by a cable 13 from a swell compensator12. The suction tube 4 can be disconnected from inlet 6 when not in use,raised by the winch cables 14 and cable 13, driven by winch 15, andstored on the deck of the vessel.

While not visible in FIG. 1, the vessel 2 has a similar suction tube 4,inlet 6, coupling 8, draghead 10, compensator 12 and winches 15 mountedon the opposite side of the vessel.

Referring to FIG. 2, which illustrates a detail side view of thefloatation draghead 10 with buoyancy, it can be seen that the suctiontube 4 is connected to a laterally extending horizontal semi-cylindricaldraghead 18, the upper end of which extends above the water level 19.The draghead 18 is hollow and the lower portion is connected to thehollow suction tube 4. The draghead 18 is partially held in positionrelative to the water line by buoyancy float 16, which typically assumesabout onethird third of the suction tube 4 and draghead 18 weight atthis point. The float 16 in turn is suspended in position by cable 13from swell compensator 12 which is connected to the deck of the vessel.The buoyancy float 16 assists in maintaining the draghead 18 at waterlevel 19. However, the main responsibility for maintaining the draghead18 in position relative to the water line 19, as seen in FIG. 2, restswith the swell compensator 12 and cable 13. The swell compensator 12 istypically a hydraulic cylinder and carries about two-thirds of theweight of the draghead 18. When the water level rises, the compensator12 takes up slack; when the water level falls, the compensator 12 lowersthe draghead proportionally. The direction of rise and fall of thedraghead 10 is indicated by double headed arrow 7. Water/oil intake isindicated by arrow 17 while water/oil travel in the tube 4 is idicatedby arrow 17A.

FIG. 3 illustrates a side view of the vessel 2 with the mid-hold sectioncut away to reveal the hold (hopper) construction in the interior of thevessel. Ten hoppers are depicted, namely, aft hopper tanks Nos. 1' to4', which are identified with reference number 25, two mid-hopper tanksNos. 5' and 6', which are identified with reference number 24, and fourforward hopper tanks Nos. 7' to 10', which are identified with referencenumber 25. A corresponding number of matching hoppers are constructed onthe opposite side of the vessel. A sand pump 20, which is positioned inthe interior of the hull of the vessel 2, and is connected to sand pumpsuction inlet 6, as shown in FIG. 1, is connected to sand pump dischargetube 22. The sand pump 20 via suction tube 4, and draghead 18 (not shownin FIG. 3), sucks in a mixture of sea water and oil from the oil spill,and discharges it through sand pump discharge tube 22. In a loweredposition, when not engaged in oil spill clean-up, the flotation dragheadwould be replaced with a standard dredge draghead which would rest onthe sea floor and the pump would suck in sand and solid material actingas a dredge.

The end of the discharge tube 22 opposite sand pump 20 discharges thepumped contents through a right angle elbow 34 directly above hoppertanks Nos. 5' and 6', as identified with reference No. 24. Acorresponding tube 22B (see FIG. 4) and pump 20B discharges pumpedcontents into the corresponding hopper tanks on the opposite side of thevessel. A pair of bottom doors 26 are located respectively at the baseof hopper tanks Nos. 5' and 6' (reference No. 24). Typically, dischargetubes 22 and pumps 20 move about a ton of water/oil per second. Thus aconsiderable volume of water/oil is moved through tanks Nos. 5' and 6'.Hopper tanks Nos. 5' and 6' are sealed from the fore and aft tanks byhaving the conventional limber holes 30 (see FIG. 5), which normallyexist between adjacent hoppers, sealed. A baffle 32 prevents excessivespill-over from the discharge tube 20, via elbow 34, into the fore andaft hold tanks 25. The fore and aft hold hopper tanks 25 also havebottom doors 28, which are closed or only partially open.

FIG. 4, which illustrates a top cut-away view of the oil/water holdhopper tanks 24 and 25 (seen as tanks 5' and 6', 15' and 16' in FIG. 4)of the vessel 2, depicts a pair of sand pumps 20, that is, port sandpump 20A and starboard sand pump 20B, connected respectively to port andstarboard suction tubes 22A and 22B, and port and starboard right angleelbows 34A and 34B. As can be seen in FIG. 4, the material dischargefrom elbows 34A and 34B are aimed directly at one another. Thisimpacting action is very important to the operation of the oil-waterseparation process because when the opposite discharges impact with oneanother, the relative velocity drops immediately to zero, the oil andwater are subjected to a dispersing and separation action and awaterfall action 36 is created. This waterfall action permits the oil toseparate from the water and instantly float at the top of the water. Themajority of the discharge with the oil floating on the top as a froth orfoam falls directly into the No. 5', 6', 15' and 16' hopper tanks 24.FIG. 4 also illustrates the pair of baffles 32 which assist in retainingthe waterfall action 36 in the No. 5', 6', 15' and 16' hopper tanks.

FIG. 5 illustrates in detailed side elevation cutaway view the specificconstruction of the fore and aft hold tanks Nos. 1' to 4' and Nos. 7' to10' , and the mid No. 5' and 6' hopper tanks 24. The bottom doors 26 areshown fully open at the base of the No. 5' and 6' hopper tanks 24. Thisis required to permit the pumped ton of water per second to pass throughthe tanks Nos. 5' and 6'. The same is true of the opposite tanks Nos.15' and 16'. The limber holes 30 are sealed in order to separate the No.5' and 6' hopper tanks 24 from the adjacent hold tanks 25. Bottom doors28, which are partially open, are located respectively at the base ofeach of the fore and aft hold tanks 25. The sand pump 20 pumps the tonper second oil/seawater mixture through sand pump discharge 22 andsubsequently through right angle elbow 34 to create the oil dispersingwaterfall effect. The discharge is depicted with reference numeral 36.As can be seen, since the waterfall action 36 virtually separates theoil from the water immediately, the oil floats on the top of the waterand passes into adjacent tanks 1' to 4', 7' to 10' , and on the oppositeside tanks 11' to 14' and 17' to 20'. FIG. 5 illustrates also how thepair of baffles 32 located under the deck 3 prevent the bulk of thedischarge 36 from dispensing into the fore and aft hold tanks 25. Thebulk of the discharge 36 is directed by baffles 32 to drop directly intothe Nos. 5', 6', 15' and 16' hopper tanks 24. The effect is that thebulk of the water passes downwardly through Nos. 5', 6', 15' and 16'hopper tanks 24, and the separated oil spillover from those tanks(primarily a highly concentrated mixture of oil relative to the water)flows into the fore and aft hold tanks 25. The oil collects at the topof the fore and aft hold tanks 25 and oil can be collected in thesetanks until the tanks 25 are full. The bottom doors 26 permit the bulkof the pumped water (a ton of water per second) to exit the bottom ofthe vessel 2. This is indicated with directional arrows 37. The floatingoil which spills over into fore and aft tanks 25 is retained and surpluswater is passed out through bottom doors 28. It should be noted that theliquid level remains even in fore and aft hold tanks 25 because thosetanks are connected by common limber holes, which are not sealed as isthe case with the limber holes 30 separating the Nos. 5', 6', 15' and16' hopper tanks 24 from the fore and aft hold tanks 25. Sea water leveloutside the vessel is indicated by line 19. The oil/water mixture pumpedinto the vessel has a positive head indicated by line 29.

FIG. 6 illustrates in detailed side view the construction of the swellcompensator 12, buoyancy float 16 system. The cable 12 passes through apair of pulleys 38. A swell compensator mechanism 40, such as ahydraulic cylinder in which the oil pressure can be adjusted to providethe proper buoyancy compensating factor, is positioned between therespective pulleys 38 and 38A. Direction of movement of the cylinder 40is indicated by arrow 39. Independently, without the compensator 12, theflotation draghead 10 would be three times the size of that shown in thedrawings. The combination of the float 16 and the compensator 12 enablesthe size of the draghead 18 to be reduced by two thirds. This buoyancycompensator system provides a substantial amount of flexibility andenables the draghead 18 to deal with rapid changes in water level 19,thereby ensuring that the float 16 and draghead 18 remain in properrelative orientation to the level of the water 19, even in rough waters.The swell compensator 40 is normally controlled to carry about 20 tonsof the draghead 18 weight which is typically about 30 tons. The buoyancyfloat 16 carries about 10 tons of the draghead weight. The swellcompensator 12 is designed to absorb fluctuations in draghead weight dueto changes in water level and permits smooth movement of the draghead 18to compensate for roll of the vessel 2 and variable sea conditions. Withproper compensator adjustment, maximum oil slick contaminant pick-up isprovided by the draghead 18, and air locks and wave carryover areminimized. As can be recognized, if the draghead 18, particularly inrough seas, spends most of its time riding either above the watersurface or below the water surface, then either mainly air or mainly seawater is sucked in through suction tube 4, which is inefficient. Theobjective is to ensure that the draghead 18 remains at water surfacelevel as much as possible so that a mixture of oil and water from theoil slick is efficiently sucked into suction tube 4. Trim changes toadjust compensator 12 action are performed by winches 15 tightening orloosening cable 11.

The buoyancy compensator 12 is designed to absorb and quickly adjust forfluctuations in buoyancy load caused by water conditions. For example,when the water level rises due to wave action, the draghead 18 wouldtend through inertia to remain stationary unless the buoyancy weight ismomentarily lightened. This is done by the hydraulic compensator 40.Thus, the draghead 18 then moves upward momentarily to thereby remain atwater level. Likewise, if the water level drops, the compensator 40makes a rapid adjustment and lets the draghead 18 drop so it follows thedropping water level. In this way, the draghead follows the rising anddropping water level caused by wave action or swells.

FIG. 7 illustrates a top view of the draghead 18 and buoyancy tank 16.The compensator cable 13 is connected to the cylindrical buoyancy tank.The draghead is in the form of a semi-cylinder with its front end openmuch like the intake of a vacuum cleaner wand, to receive the oil-watermixture, which is then sucked into tube 4.

It is very evident that the scale of equipment necessary to clean upcatastrophic oil spills of millions of liters of petroleum must be equalto the degree of the spill. The equipment must be capable of handlingtons of water per second in order to clean up the spill as rapidly aspossible and thereby minimize environmental damage. It is also veryevident that the equipment presently available world-wide has limitedclean-up and salvage capabilities with moderate spills and no successwhatsoever with major spills.

Specifications for equipment required to successfully clean up oilspills are as follows:

1. A floatation draghead pick-up capability within a boomed area anddirect transfer to a large storage tanker;

2. A floatation draghead pick-up swath path clean-up of at least 33meters;

3. A minimum continuous 6 knot operational capability, in order toachieve an actual area clean-up of 400,000 m² /hour, or 1 sq. mile/10hours;

4. A pumping capacity of at least 4,000 m³ /hour;

5. A continuous 4,000 m³ /hour contaminant separation system;

6. A minimum salvage operation capability in worst weather conditions of10 ft. wave action;

7. A number of salvage oil holding tanks of 2,000 m³ capacity;

8. A vessel capable of working dangerous navigational waters andconfined wreck areas, including an experienced crew and modern dredgevessel equipment; and

9. A dual role dredge/oil slick salvage vessel.

A successful oil spill clean-up operation network should includestationing vessels in all sensitive areas and having the capability todeliver equipment on accident site within twenty-four hours, and amandatory back-up vessel available within a further twenty-four hours tocover both major spill containment and oil slick clean-up.

The swath path clean-up is governed by the vessel's beam plus theextension of port and starboard floatation draghead width. It should benoted that a vessel with a 33 meter swath path and speed of operation,namely, a minimum 6 knot clean-up, is capable of dealing with virtuallyall supertanker oil spills, major or minor.

When a vessel of 5,000 tons moves through the water at 6 knots, the5,000 ton water displacement aft has the effect of pulling surface waterto the vessel's hull thus increasing the actual swath path contaminantby perhaps 50 percent.

The massive pumping capacity of the sand pumps of the vessel makes itpossible through the two suction floatation dragheads 18 to cope easilywith a typical 95 percent water, 5 percent oil slick pick-up analysis inorder to minimize environmental damage. Speed is of the essence. It isnot possible to have a swath path of 400,000 sq. m./hr. (1 to 2 tons ofwater containment per second) clean-up ability achieved by changing theoil/water percentages significantly. This fact makes the oil/waterseparation process most significant in the solution to the clean-up andsalvage of all large marine oil release accidents.

A hopper tank capacity of at least 2,000 m³ for salvage oil storageallows a normal clean-up of oil slick areas of approximately 2 sq. milesin about a time of twenty hours before a transfer of salvaged oil to astorage tanker is required. It should be noted that for initial oilslick containment where a boomed damage control accident has occurredand oil slick depth is excessive, pick-up by the floatation draghead ofthe invention within such a boomed area and direct transfer to a largestorage tanker is desirable, possible, and effective with the inventionthat is disclosed herein.

To effectively ensure against oil spill disasters, it should be arequirement that all vessels carry sufficient boom length on board toencircle the vessel one and a half times so as to contain any oilleakage to a depth of one foot. This system can be put in place quicklyto initially contain the spill until oil slick salvage vessels canarrive.

The invention pertains to a system and equipment for enabling a trailersuction dredge vessel to act as an oil slick salvage vessel, whenrequired. The vessel thus has a dual role and can be operatedeffectively as a dredge in order to meet costs of operation while havingthe capacity to function as an oil spill clean-up vessel when theoccasion demands.

The port and starboard sand pump discharges 22A and 22B are adjusted toperhaps 50 percent capacity and are directed to the midship hopper 24discharge station. 90° elbow fittings 34A and 34B are attached to bothdischarge outlets so that the discharge flow is diverted thwartships andinto direct opposing contact thereby causing two effects. The solid sandpump discharge flow pressure of 2 bar, capacity 50 m³ /min. (a ton ofwater per second), provides an atomising action which breaks up(separates) the oil slick contaminant elements. The second effect isthat the discharge flow velocities of the two pumps 20A and 20B byimpacting one another directly reduce the relative discharge velocity tozero. This converts the flow discharge action to a deluge or waterfallaction. The oil-water separation is accomplished by the deluge orwaterfall action which, because of the high discharge velocity from eachdischarge elbow impacting each other and reducing the net velocity tozero, causes the oil to disperse into tiny droplets. These oil droplets,because of the lighter specific gravity and coalescing action, do notpenetrate appreciably into the water surface. The falling water, on theother hand, because of heavier specific gravity and lower coalescingaction, penetrates well below the surface level. Thus a naturaloil-water separation action is set up by the waterfall.

The reduction to effective net zero velocity also has the benefit thattremendous currents which would otherwise occur in the hoppers areeffectively nullified, thereby enhancing the oil-water separationaction. The effect of this is that the oil is dispersed into tinydroplets which immediately separate from the water and float as a foamor froth as the discharge falls to the top surface of the water in thehoppers.

The volume discharge through the bottom doors 26 of Hopper Nos. 5', 6',15' and 16' should be about 0.45 meters ullage per minute to enable thewater pumped into those hoppers to pass from the holds and maintainproper oil froth-water level in those hoppers. This slow rate of tankdischarge through bottom doors 26 where a tank sounding of 8.5 meters ismaintained guarantees that all oil contaminant remains as a froth on thewater surface and can be directed to the forward and aft tanks 25 bydeluge and floating action and stored there. Tanks 25 typically wouldhave a bleed discharge of about 5 percent pump volume through the bottomdoors 28. The discharge rate through bottom doors 28 can be increased ordecreased if the oil/water interface of the oil slick calls for it. Theoil collected in the forward and aft tanks 1' to 4', 7' to 10', 11' to14' and 17' to 20' will increase with time as more oil-water is passedinto those tanks. When the tanks are 90 percent full of oil, the tanksare unloaded into an awaiting tanker.

The swell compensator 12 is designed to maintain a predeterminedconstant controlled load of about 10 tons on the draghead when dredgingon the sand or gravel pit floor (sea bottom). This representsapproximately 1/3 of the total draghead 18 and suction tube 4distributed weight. It is possible for the draghead 18 to maintaincorrect water surface position by designing a floatation draghead 16 and18 so that the buoyancy carries this constant load with a margin ofsafety of, say, 20 percent. The swell compensator 12 then gives fast,smooth hunting control that is necessary for all ship movements and seaconditions. This allows maximum oil slick contaminant pick-up by thesand pump suction and eliminates air locks and wave carry over.

If apparatus according to the invention had been available with respectto the recent Valdez spill accident, the slick could have been containedin the initial stages. Salvage vessels according to the invention can bedesigned to have a potential containment equal to any boomed damagecontrol area. However, it should be noted that great improvement indesign must be made with booms so as to contain oil spills to a muchlarger depth and capacity. The potential clean-up capacity of theinvention of one sq. mile/10 hours would be sufficient to cope with anymoderate spill. It should be remembered that on exceptionally large(major) spills, containment control would be maintained until othersalvage vessels of the same potential capacity arrive on site.

Previous thinking regarding capital costs involved to have fully mannedsalvage vessels of a size capable of dealing with major oil spillsstationed at perhaps 500 mile coastal intervals throughout sensitiveareas are generally seen as prohibitive. However, since the dual roletrailer suction dredge oil slick clean-up vessels are fast 16 to 18 knotships, they can be allowed to undertake dredge contracts in theirallotted area. This would offset, if not cover, all operational expensesincurred. The conversion to oil slick/containment salvage can becompleted easily in the twenty-four hours enroute to the accident site.

As will be apparent to those skilled in the art in the light of theforegoing disclosure, many alterations and modifications are possible inthe practice of this invention without departing from the spirit orscope thereof. Accordingly, the scope of the invention is to beconstrued in accordance with the substance defined by the followingclaims.

I claim:
 1. A method of separating oil from an oil-water mixture whichcomprises directing two flows of an oil-water mixture from substantiallyopposite directions against one another and at substantially equalvelocity, without intervening baffles between the two flows and at aposition above a container, the two flows being directed against eachother at a velocity sufficient to disperse the oil into small particlesand to reduce the net velocity of the opposed flows to substantiallyzero, whereby the oil and water of the two flows fall into the containerwith a substantial number of the oil particles floating on the surfaceof the water within the container.
 2. The method according to claim 1further including the step of discharging the water within the containerfrom below the surface and conveying the small floating oil particlesfrom the surface to an adjacent container.
 3. A method according toclaim 2 wherein the containers are located in a ship hull.
 4. A methodaccording to claim 2 wherein the oil and water of the two flows fallinto a plurality of primary containers and the small floating oilparticles and a portion of the water are conveyed to a plurality ofsecondary containers adjacent the primary containers.
 5. A methodaccording to claim 4 wherein separated water is discharged from thebottoms of the primary and secondary containers.
 6. A method accordingto claim 5 wherein the primary and secondary containers areinterconnected below the surface of the water.